Thermal responsive device



Filed l larch 22, 1923 at 4 ,6 /7 A9.

' ii j'T' 9 I A A entor:

yM f H i S Attorwey.

Patented June 2, 1925. 7

UNITED STATES PATENT oFFicE.

CHESTER I. HALL,'OF FORT WAYNE, INDIANA, ASSIGNOR TO GENERAL.ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

THERMAL RFSPONSIVE DEVICE.

Application filed March 22, 1923. Serial No. 626,906.

'1' all whom it may concern:

Be it known that I, Crus'rm I. HALL, a citizen of the United States, residing at Fort lVayne, county of Allen, State of Indiana, have invented certain new and useful Improvements in Thermal Responsive Devices, of which the following is a specification.

Onc of the objects of my invention is to provide a thermal protective device, 'parti cularly adapted for use with alternating -current circuits to protect a translating de-' vice connected to the circuit from conditions caused by unbalancing of the phases.

A further object of the invention is to provide an improved thermal protective device for protecting'a translating device connected to an electric'circuitfrom overloadsor other conditions which would cause overheating.

A still further object of the invention is to provide aprotective device for protect ing a translating device connected to an electric circuit from conditions caused either by an unbalancing of the phases of the circuit or from overloads or other conditions which would cause overheating.

These and other objects of the invention are attained in the device which is illustrated in 'very diagrammatic'form in the accompanying drawing and which is hereinafter fully described. V

In carrying the invention into effect in one form, I provide a protective device having a plurality of thermally sensitive or thermally responsive elements which are so arranged as to be energized responsively to the currcnt'in the separate phase conductors, so that the elements will be heated in accordance with the current in the respective phase conductors and the respective heating 'c-ll'ccts or their respective movements due to their heating eflects willtherefore be proport ioual to the square of the current values flowing in the conductors of the multiphase ('il'cuit. If the current in one phase differs by some predetermined amount from the current in other of the phases, the ditlercnccs between the heating effects or the difference between the deflections or the difference between the movements of a portion of the elements will be a predetermined value. Switch mechanism is arranged to be controlled by the thermal responsive elements so as to protect the controlled circuit. The arrangement is preferably such that a pair of switch contacts which are normally closed will be opened in response to a predetermined relative movement of the thermal responsive elements when-thephase unbalancing occurs. The controlling switch contacts may be arranged so as to automatically effect the opening of a controlled circuit or to give a signal whereby an attendant may open the circuit. Furthermore, the arrange ment may be such thatthe permissible degree of unbalancing of the phases may be adjusted. In' general, the device may with advantage beset for a phase unbalance of 10 per cent to 25 per cent at full load on the translating device protected. The arrangement will be such that the controlling contacts of the device'will be maintained closed in case the unbalance of the phases with full load in the circuit is not greater than the predetermined-amount. A greater unbalance than the predetermined amount will cause the contacts toopen in a certain length of time, this time varying inversely with the difi'erences'of the squares of the respective current values in the thermal responsive elements The length of time required at a given load or percentage unbalanced condition will of course depend upon the thermal time lag of the device. This will ordinarily be made as short as practicable, although it may be also made to duplicate the thermal characteristics of the machine. Upon complete phase unbalance, that is, single-phase operation of a polyphase machine, a portion of the elements will be completely deenergized, and the remainder of the thermal responsive elements will be caused to deflect or move in response to something more than the full load current, so that opening of the contacts will occur very promptly. The device may be also used to protect a translating device from conditions caused by overheating as well as to protect the device from phase uubalance conditions, and in accordance with this feature of the invention, the arrangement is preferably such that a predetermined simultaneous movement of the thermal responsive elements will effect the opening of the contn lled contacts, so as to there'- by either automatically disconnect the translating device from the supply circuit orto give an indication of the fact that the translating device should be disconnected from the-supply circuit.

For a better understanding of the invention, reference is bad to the accompanying drawing in which Fig. 1 is a plan view of a protective device in accordance with the invention; Fig. 2 is a cross section taken on the section line 22, Fig. 1; Fig. 3'is a very simplified diagram showing the protective'device in accordance with the invention used for the protection of a polyphase alternatin current electric motor. 7

Re erring to the drawings, it will be seen that the protective device is shown as a device for the protection of three-phase alternating current circuits, but it will be understood that my invention is not necessarily limited to a three-phase protective device, since the invention is applicable to the protection of other polyphase circuits.

The device as shown comprisesthree thermal responsive elements 10,11and 12 which are arranged so that one end of eaehelement is fixed, and the other end of the element Tis free to move and is positioned adjacent the free ends of the other elements. Thus, the element-11 is secured at one end in the insulating block 13, and the free end of this element is adjacent the free ends of the .elements 10 and 12. These elements may be each in the form of thermostatic stripsas customary in the art, thatis', the elements may be each composed of two bi-metallic strips suitably joined together, sowhen the element is heated a deflection is produced due to theuncqual expansion of the one part of the strip with respcctcto the other part of the strip, although the invention is not necessarily limited to the employment of thermostatic strips. Bi-metallic thermostatic elements and thermal responsive elements in general are well known in the art, and -it is believed that no further description thereof is herein necessary. It will be observed that each of the thermostatic elements is arranged so as to be a conductor which may be included in 'one of the phase conductors of the circuit, or to be otherwise energized in accordance with V the circuit in a respective phase conductor,

control of the thermostatic elements, so as to either give a visible indication of the fact that the phases are unbalanced or overfrom the pivotally mounted member 17,

and the contact 15 is secured to and insulated from the pivotally mounted member 18. The members 17 and 18 are each pivotally mounted on the posts 19, only one of which is shown in Fig. 2, and the deviceas a whole is mounted on the insulating base shown.

The adjustment of the permissible degree of. phase unbalance is accomplished by means of an. ad usting device for each of the thermostatic elements.

11 is shown asof a form in which an adjusting screw 20 is connected with the pivoted member 17 and an ad usting screw 21 is connected with the pivoted'membcr.

18,- and these adjusting screws are arranged to cooperate with the free end of the element 11. These adjusting screws 20 and 21 may be adjusted so as to.be separated by a predetermined amount so as to thereby permit By reference to- Fig. 2, the adjusting device for the element the free end of the element 11 to move or deflect relatively to the other elements without etl'ecting any relative movement between the member 17 or the member 18, and thus without having any movement of thecircuit controlling contacts 11 and 15. However, when the relative deflection of eleme .t. 11 exceeds a predetermined amount, the free end thereof engages either with screw .20 or-scrcw 21 depending upon the direction of deflection and thereby moves cithcrthc member 17 or the. member 18 to separate the contacts 14 and 15. the other member 18 or 17 being held by the elements 10 and 12. A similar adjusting device 2;. is provided for the element It). and a similar adjusting device 23 is provided for the clcmcnt 12. These adjusting devices make possible an adjustment of all three of the. elements to precisely the same condition. so that a predetermined relative ll'l()\'(tll(lll of any element with respect to another is requircd to etiect. relative movement bet ween the members 17 and 1S and the consequent. separation of contacts 14 and 15.

'ith the. adjustment so made that the two sets of screws are practically in contact with the thermostatic metal strips 10, 11 and 12, on both sides thereof, a very slight unbalance will cause the opening of the circuit controlling contacts 14. and 15. However. if the contacts are adjusted so that the two sets of adjusting screws are quite far apart,

' tinuation of the deflection ofthe thermo to deflect back and forth, movingthe two pivotally mounted members 17 and 18 simultaneously and moving the adjustingdevice and the contact, mechanism freely as a unit, and there will thus be no separation of. the contact mechanism until the phase unbalance is greater than the predetermined value. It

will thus be seen that in the'protection of a stantially similar movement of the thermotranslating .device, as long as there is substatic elements, there will rbe no operative etiect of the device, but \vhen the relative movement of .the thermostatic element is greater than a predetermined amount the relative movement will cited: the opening of the contacts controlled by the device.-

In .order to provide for protection against overloads, I have providedthe adjustable stop '24 which cooperates with the pivoted member-18 and the adjustable contact 15.

In case the thermostatic elements should move the "switch condemn-and 15 as'a unit" "greater than a predeterminedamount, the .end of the pivoted member 18 willengage the adjustable stop '24 so 'as to arrest the further movement of the contact 15. A constatic elements will cause the contact 14 to be se arated from the contact 15, even thong i there is no unbalancing of the phases.

respective conductors.

Overloads are thereby protected against.

Referring to Fig. 3, it will be seen. that I have shown my protective device used for the protection of an alternating current motor M which is arranged to be connected to the three-phase source of supply 25 by means of the circuit breaker shown very diagranunatically. The thermostatic elements [0, II and 12 are each included in a phase conductor, so that the heating of the respective elements will be in accordance with the current in the The contacts ll and 15 are arranged to be includedin the. coil circuit of a holding electromaguet 36 on the. circuit breaker, and the arrangement. is such that the circuit breaker will he held closed under the control of the eleetromagnct. :26. \Vhen the contacts 14 and 15 separate. the electronlagnet 26 will he decnergized and the circuit, breaker will be permitted to auto-. matically open in a manner well understood by those skilled in the art. The motor M will thus be protected from phase unbalancing, from phase failure and'from overload, as will he understood from a consideration of the description of the device shown in Figs. 1 and 2.

In accordance with the provisiousof the patent statutes, I have described the principle of operation of my invention, togetner with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is,-.

1, A protective device for electric circuits comprising circuit controlling switch mechanism, a plurality of thermal responsive movable elements for controlling the said switch mechanism, each of said elements adapted to be heated in accordance with the current 111 a separate conductor of the protected circuit and the said elementsarrangedv to operate the said switch mechanism in response to the relative movement of said-elements. 7

2. A protective device for electric circuits comprising circuit controlling switch mechanism, a plurality of thermal responsive mov- I able elements, each of said elements adapted to be heated in accordance with the current in a separate conductor of the protected circuit, and means opera'tivelyconnecting said elements with said mecha'msm to operate the said elements.

3. A protective device for electric circuits comprising circuit controlling switch mechanism, a plurality of thermal responsive movable elements for; controlling the said switch mechanism, each ofsaid elements adapted to be heated in accordance with the current in a separate conductor of the protccted circuit and the said elements 4 arranged to jointly operate the said switch mechanism in response to the movement of said elements due to a predetermined .value of current 'n the said conductors.

4. A pre ective device for electriccircuits comprising circuit controlling switch mechanism, a plurality of thermal responsive movable elements, each of said elements adapted to be heated in accordance with the current in a separate conductor of the protected circuit. and means operatively connecting said elements with said mechanism to operate the same rcsponsively to relative movement of said elements and to joint movement of said elements.

5. A protective device for electric circuits comprising circuit controlling switch mechanism, a plurality of thermal responsive movable elements for controlling the said switch mechanism, each of said elements adapted to be heated in accordance with the current in a separate conductor of the protected circuit and the said elements arranged to operate the said switch mechanism in response to the relative movement of said elements due to an unbalancing of the current in the respective conductors of the protect.-

samere'sponsively to relative movement ofthe conductors,

ed circuit, and means for adjusting the degree of unbalancing of the current in the conductors of the controlled circuit necessary to effect the operation of said switch mechanism.

6. A rotective device for electric circuits comprising a plurality of thermal responsive elements, each of said elements adapted to be heated in accordance with the current in a separate conductor of the protected circuit, the said elements arranged to move submovable elements for controlling the said switch mechanism, each of said elements adapted to be heated in accordance with the current in aseparate conductor of the protected circuit and the said elements arranged to operate the said switch mechanism in response to either the relative movement of the elements due to an unbalancing of the current'in said conductors or in response to the combinedmovement of said elements due to a predetermined value of current in the said conductors.

8. A phase unbalance protective device for electric'circuits comprising a plurality of-thermal responsive movable elements, each of said elements energized responsivcly to the current in a separate conductor of the circuit controlled by the device, and switch contact mechanism operated by the relative lllOVtl'lKllt of the said elements for opening the electriccircuit in response to a predetermined unbalancing of the phases.

9. A phase unbalance protective device for electric circuits comprising a plurality of thern'iostatic elements, each having a free end adapted to move in accordance with the heating etlect of the current in a separate conductor'of the circuits controlled by the device, and switch contact mechanism operated by the. relative movement of the free ends of said elements for opening the electric circuit in response to a predetcr mined unbalancing of the phases.

10. A phase unbalance protective device for electric circuits comprising a plurality of thermal responsive movable elements. each of said elements energized.i'esponsively to the current in a separate conductor of the circuit controlled by the device, and a pair of switch contacts normally biased to closed position and movable in unison by the said elements when the current in the respective phases of the controlled circuit varies subtially similar variations of the current in.

the phases of the protected circuit and movable relatively to each other in response to an unbalancing of the currentin the phases, and circuit controlling switch mechanism arranged -to be operated in response to either a predetermined simultaneous movement of the said elements or in response to a predetermined relative movement of the elements.

12. A phase unbalance and overload pro-- tective device for electric circuits comprising a plurality of thermal responsive elements, each of said elements adapted to be heated in accordance with the current in a separate conductor of the protected circuit,

the said elements arranged to move substantially simultaneously in response to substantially similar variations of the current in the phases of the protected circuit and movable relatively to each other in response to an unbalancing of the current in the phases, and circuit controlling normally closed movable switch contacts connected to the said elements to be moved thereby as a unit through a limited distance and to be separated by either a. relative movement of the elements or a s ultaneous movement of the elements great than the said limited distance.

13. A protective device for cuits comprising a plurality of thermostatic elements, each of said elements having one end fixed and the other end thereof free to move in accordance with the heating effect of the current in a separate conductor of the circuit to be protected, adjustable switch contacts arranged to be operated in accordance with the relative movement of the free' ends of the said elements, and means for ad justing the percentage of unbalancing of the current in the conductors of the controlled circuit necessary to effect the opera-' tion of said contacts.

14. A protective device for electric cira-trio circuits comprising a plurality of thermostatic elements, each of said elements having one end fixed and the other end thereof free to move in accordance with the heating effect of the current in a separate conductor of the circuit to be protected, a pair of normally closed adjustable switch contacts, and apivotally mounted member for supporting each of the said contacts and cooperating with the free ends of the said elements to separate each the said contacts due to the relative move ments of the free ends of the elements occasioned by an unbalancing of the currents in the said conductors.

15. A protective device.for electric circuits comprising a plurality of thermostatic elements, each of said elements having one end thereof fixed and the other end thereof free to move in accordance with the heating effect of. the current in a separate conductor of the circuit to be protected, a pair of normally closed adjustable switch contacts, a pivotally mounted member for supporting of the said contacts and cooperating with the free ends of the said elements to separate the said contacts due to the rela tive movements of the free ends of the elements occasioned by unbalancing of the current in the said conductors, and means for adjusting the percentage of unbalancing of the current in the conductors of the controlled circuit necessary to effect the opening of said contacts.

16. A protective device for electric circuits comprising a plurality of thermostatic elements, each of said elements having one end thereof fixed and the other end thereof free to move in accordance with the heating effect of the-current in a separate conductor of the circuit to be protected, a pair of normally closed adjustable switch contacts, a pivotally each of said contacts and cooperating with the free ends of the said elements to separate the said contacts due to the relative movements of the free ends of the elements 0ccasioned by an unbalancing of the current in the said conductors, an adjusting device cooperating with each of the said pivotally mounted members for adjusting the percentage of unbalancing of the current in the conductors necessary to effect the opening c. the said contacts,and an adjustable stop cooperating with one of said pivotally mounted members i for limiting the movement thereof to eifect the opening of the said contacts due to a predetermined simultaneous movement of the free ends of said elements.

In witness whereof, I have hereunto set my hand this 19 day of March, 1923.

CHESTER I. HALL.

mounted member for supporting 

